Auto merge of #19323 - asajeffrey:test-perf-run-nightly, r=edunham

Run test-perf on linux-nightly.

<!-- Please describe your changes on the following line: -->

Run test-perf on linux-nightly.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12988
- [X] These changes do not require tests because this is test infrastructure

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/19323)
<!-- Reviewable:end -->

etc/ci/buildbot_steps.yml

@@ -113,6 +113,7 @@ linux-nightly:
   - env CC=gcc-5 CXX=g++-5 ./mach build --release
   - ./mach package --release
   - ./mach upload-nightly linux
+  - ./mach test-perf --submit
 
 android:
   - ./mach clean-nightlies --keep 3 --force